Apparatus for and method of milking an animal

ABSTRACT

Transducers 114 are acted upon by milk flowing respectively from each teat of the animal into a milking claw which has an upper chamber 119 and a lower chamber 120. The transducers respond to a condition of the milk and control valves 128. If the transducer indicates normal milk, valve 128 is set to direct flow into the lower chamber 120 from which it passes via pipe 122 to a collection tank. If abnormal milk is indicated, valve 128 is set to direct flow into the upper chamber 119, from which it passes via pipe 124 to a dump bucket or drain.

The invention relates to apparatus for and a method of milking an animaland is concerned with the automatic provision of information about theanimal during milking by monitoring the milk and detecting a monitoredcondition in the milk, if such condition arises.

An electrical measuring device is known from German patent specificationDE 1949559 for examination of milk during milking forpathological-changes, in particular changes indicative of mastitisinfection. Measuring transducers, responding to the conductivity and/orpermeability and/or the dielectric constants of the milk, are arrangedto monitor milk originating from different teats of the animal beingmilked.

One problem is the provision of a reference standard because thementioned properties of the milk, even when normal, will vary from oneanimal to another, from one day to another and in dependence upon thefood the animal has been eating. The solution proposed by DE 1949559relies upon the observation that it is common for mastitis to affect, atleast initially, only one of the four teats of the udder. Accordingly DE1949559 arranges the four transducers in a bridge circuit, which goesunbalanced if the conductivity of the milk from one teat changes withrespect to that from the other three teats. There is, however, noindication of which teat is the source of milk of changed conductivity.

An appreciation on which the present invention is based, is the conceptof rapid automatic indication of which path is carrying milk from aninfected teat, and further, providing automatic control to divert theoutflow of such milk when detected. For realisation of these conceptsnew solutions have been devised for the provision of both a referencestandard and adequate detection sensitivity.

In accordance with the present invention, in one of its aspects, thereis provided apparatus for use in the milking of an animal whichcomprises a plurality of inlet paths and a common outlet path, arespective transducer associated with each inlet path for providing aquantitative signal representing the magnitude of a property of milk inthat path, comparison means for comparing the said signal in each inletpath with a reference, characterised in that the comparison meansprovides an output signal which identifies the inlet path in which themilk has a magnitude of the said property differing by more than apre-determined amount from the reference magnitude.

For automatic control of the outflow of milk in response to suchcomparison, a subsidiary outlet path is provided, and each of the saidinlet paths is provided with a valve capable of diverting flow from theinlet path away from the said common outlet path to the subsidiaryoutlet path. Preferably control means responsive to the said outputsignal actuate the valve in the input path identified by the outputsignal to divert flow to the said subsidiary outlet path. Conveniently,the control means is so arranged that, during an initial stage ofmilking, the valves direct milk from all the inlet paths to thesubsidiary outlet path and, at the end of the initial stage, some or allof the valves are operated to direct milk from the corresponding inletpaths to the said common outlet path.

The said reference is preferably generated by reference means as anaverage of the signals representing the respective magnitudes of theproperty of the milk in the inlet paths. The monitored condition may bethe presence in the milk of a substance which is one of the groupcomprising progesterone, pheromone and substances resulting from theoccurrence of mastitis in the animal or an abnormal concentration ofsuch substance in the milk. The monitored property may be electricalconductivity or some other property of the milk and the indication maybe provided when the value of the property falls below or exceeds athreshold value.

The milk may be monitored by determining the effect of the milk onenergy applied to the milk. The energy may be electromagnetic energy,alternatively, the milk may be monitored by monitoring the value of anelectrical property of a device which is exposed to the milk or tosubstances from the milk.

The milk may be monitored by means of a known technique for detectingthe presence of specific, organic substances.

Preferably, the milk is monitored continually during at least asubstantial part of the milking process.

Preferably at least one of the transducers is a non-intrusive transducerand preferably the or each transducer comprises a plurality ofelectromagnetic inductors arranged to be electromagnetically coupled bymilk in the corresponding inlet path.

In one arrangement according to the invention the or each transducercomprises a pair of toroidally wound coils arranged so that the milkforms an electrically conducting loop threading the toroids formed bythe toroidally wound coils. To minimise coupling between the respectivecoils other than that provided by the milk, the coils are contained in,but electrically insulated from, appropriately toroidally shapedcontainers made from electrically conducting material, preferablycopper. The containers are open at one end in a plane parallel with theplane containing the continuous axis of the toroid. It is convenient tomount each pair of containers adjacent, but electrically insulated from,one another on the same major axis but back to back, that is with theirrespective open ends remote from one another.

With such an arrangement, measurement may be carried out by connectingan electrical power supply to provide an alternating current drive tothe drive coil and connecting an electrical signal detection circuit todetect the amplitude of the alternating current induced in the detectioncoil.

According to a further aspect of the invention each coil is a componentof a resonant circuit and the said detection circuit is connected tocontrol the power supply so as to maintain the frequency of thealternating current drive to the drive coil at or close to the resonantfrequency of the circuit containing the detection coil.

The invention also provides a method of milking an animal wherein milkfrom respective teats of the animal is monitored and, if no abnormalcondition is detected, then milk from all teats of the animal isdirected along a common, main path and, if an abnormal condition in themilk from a teat is detected, milk from that teat is directed along asubsidiary path whilst milk from the other teats is directed along thecommon, main path.

Preferably milk is drawn concurrently from a plurality of teats of theanimal, a property of milk drawn from each teat is compared duringmilking with the same property of milk drawn from each other teat and,whilst said property has substantially the same value for all of theteats, the milk drawn from all of the teats is directed along a commondischarge path and, if the value of said property of the milk from oneteat departs substantially from the value of said property of the milkfrom the other teat or teats, the milk from either the one teat or theother teat or teats is diverted from the common discharge path.

Once the milk from one teat or from the other teat or teats has beendiverted from the common discharge path, it is preferred that diversionof the milk from that teat or from the other teat or teats from thecommon discharge path is maintained, irrespective of whether the valueof said property of the milk from the one teat reverts to a valuesubstantially the same as the value of that property of the milk fromthe other teat or teats.

Specific constructions of apparatus and methods embodying the inventionwill now be described by way of example and with reference to thedrawings filed herewith, wherein:

FIG. 1 is a perspective view of a milking claw,

FIG. 2 is a cross-section through the claw of FIG. 1,

FIG. 3 is a diagrammatic representation of a known arrangement forillustrating the principle of operation of an electrical detectionapparatus,

FIG. 3a is a representation of the equivalent electrical circuit of FIG.3,

FIG. 4 is a part sectional view of another milking claw containing anelectrical detection apparatus,

FIG. 5 is a circuit diagram of part of the electronic circuitry of theapparatus,

FIG. 6 is a circuit diagram of another part of the electronic circuitry,

FIG. 7 is a circuit diagram of a further part of the electroniccircuitry,

FIG. 8 is a part-sectional diagrammatic representation of a modificationof the milking claw of FIG. 4.

FIG. 1 shows that part of a milking machine which is referred to as the"claw" and is suitable for use in the milking of a cow having an udderwith four teats. The claw has tubes 110 to 113 which lead to known teatcups (not shown) which are applied to the teats of a cow for milking.The tubes 110 to 113 lead via respective transducers 114 to 117 to ahollow housing 118 which is divided into upper and lower chambers 119and 120 by a partition 121.

A main pipe 122 leads from the chamber 120, via a transducer 123, to amilk treatment device, for example a cooler, and a milk storage tank. Apipe 124 leads from the chamber 119 via a transducer 125 to a dumpbucket (not shown) or a drain. Pulse tubes are omitted from the drawingfor clarity but may be arranged in known manner.

Inside the housing 118, the tube 110 divides into branches 126 and 127which lead respectively into the chambers 119 and 120. A valve 128represented diagrammatically in FIG. 2 is provided to direct milkentering the housing 118 along the tube 110 into either the branch 126or the branch 127. An electrically energisable actuator (not shown) isprovided for moving the valve 128 to a selected position. Each of thetubes 111, 112 and 113 is provided with branches corresponding to thebranches 126 and 127 and with a valve corresponding to the valve 128.

The transducer 114 is adapted for applying energy to the milk and meansis provided for monitoring the effect of the milk on the applied energy.The transducer 114 may be a known device for applying electromagneticenergy to the milk which flows along the tube 110 and known means forresponding to the effect of the milk on the applied energy. Theoperation of the transducer 114 may be based on a known technique fordetecting the presence of specific, organic substances. The transducer114 may be other than a transducer for applying energy to the milk. Thetransducer 114 may be an electrical device, a property of which isaffected by one or more specific substances which may be present in themilk. For example, the device may be an ion sensitive field effecttransistor. Alternatively, the device may be arranged for carrying outchromatographic analysis of the milk. The passage for flow of milk pastthe transducer may be arranged to exclude air bubbles from a part of thepassage in the vicinity of the transducer.

The transducers 115, 116 and 117 may be identical with the transducer114. The transducers 123 and 125 may differ from the transducers 114 to117 but each may be one of the kinds of devices mentioned above. Thetransducers 123 and 125 may be adapted for determining the presence ofone or more specific substances whilst the transducers 114 to 117 areadapted for detecting the presence of one or more different substances.However, in an arrangement in which each of the transducers 114 to 117is capable of detecting the presence of each substance which is to bemonitored in the milk, then the transducers 123 and 125 may be omitted.

The transducers 114 to 117, 123 and 125, or some of these transducers,are connected with a processor (not shown) for processing signalsprovided by the transducers. The processor may be incorporated in thehousing 118 or may be at a central station remote from the housing. Inthe latter case, the processor is preferably arranged to process signalsreceived from a number of claws identical to or similar to the claw ofFIGS. 1 and 2. The central station may include one or more indicators,for example a device providing a visual indication of an abnormal orseasoned condition, and preferably includes means for recordinginformation derived from the several claws.

In one example of a method embodying the present invention, theapparatus of FIGS. 1 and 2 is used in the milking of a cow. Initially,the valves are set to divert milk from each teat into the chamber 119,during an initial stage of milking, which may last for only a fewseconds, the fore milk is discarded. Also, during this initial stage ofmilking, the milk from each teat is monitored by the transducers 114 to117 for the presence of substances which are produced by mastitis in theudder of the cow. If no such substances are detected, then, after theinitial stage of milking, the valves are operated to divert the milkfrom all of the teats into the chamber 120, from which it flows to thestorage tank.

If, during the initial stage of milking, the presence in the milk fromone teat of a substance which results from mastitis of the udder isdetected, then the milk from that teat is not diverted to the chamber120, but continues to flow to the chamber 119, from which it isdiscarded. Milk which is contaminated by the occurrence of mastitis inthe cow is thus prevented from reaching the chamber 120 and the milkstorage tank.

In this example, the monitoring is carried out only during the initialstage of milking and the valves then set, according to the result, forthe duration of the milking of the particular animal on that occasion.Whilst it is possible for the apparatus to be set to continue to monitorfor the duration of the milking process, this has been found to beunsatisfactory in that milk ceases to flow at different times fromdifferent teats. As the flow from one teat diminishes, air entering themilk in the region of the transducer will change the output and may leadto a false indication.

One property of milk which is affected by the presence of a substanceresulting from mastitis is the electrical conductivity. Thus, in aparticular example, the transducers 114 to 117 may be transducers whichprovide an electrical signal which represents the electricalconductivity of the milk. The signals from the transducers 114 to 117can be compared electronically to provide a comparison of the electricalconductivity of the milk from each teat. An output from the electroniccomparison can be used to provide automatic control of actuation of thevalves 128.

Additionally, manually operable or remotely operable means may beprovided for controlling actuation of the valves 128 and this mayover-ride automatic control. Provision is made for resetting the valvesafter manual operation.

In another embodiment, the transducers 114 to 117 may be adapted toprovide signals representing the concentration of ions, for examplepotassium ions, sodium ions or hydrogen ions, or to provide a signalindicating the concentration of nagase in the milk.

In another embodiment transducers 114 to 117 are adapted for providingsignals which indicate the presence of or the concentrations of othersubstances in the milk, for example progesterone and pheromone. Thepresence of these substances in the milk provides an importantindication about the condition of the cow and comparison of theconcentrations in the milk from different teats may not provideadditional useful information. Thus, such a transducer provided at 123or 125 could be used to obtain this information.

FIGS. 3 to 7 illustrate an apparatus embodying the invention in whichelectrical conductivity of milk is monitored so as to provide anindication of the presence of a substance resulting from mastitis.

FIG. 3 illustrates the known principle upon which the electricaldetection apparatus of this example is based. Two toroidally wound coilscomprise windings on a former which may best be visualised as arectangular section straight rod on which windings extend from one endto the other, and the rod is then bent so that its ends join and itsaxis (the continuous axis) forms a circle. A medium 11, whose electricalconductivity is to be measured, is arranged to form a conductive loopthreading the two coils which provide respectively a drive coil 12 and adetection coil 13.

If the drive coil 12 is excited with an alternating electrical current,the conducting loop 11 of the test medium will provide coupling bytransformer action with the detection coil 13. The degree of couplingbetween the drive coil 12 and the detection coil 13 is dependent uponthe conductivity of the conducting loop 11. A measure of thisconductivity can thus be derived from measurement of the current inducedin the detection coil 13.

Whilst, in principle, the magnetic field produced by toroidally woundcoils is wholly contained within the toroid, precautions must be takento ensure that there is no coupling, or substantially no couplingbetween the drive coil and the detection coil except that provided viathe loop of conductive medium 11.

FIG. 3a represents schematically the equivalent circuit of FIG. 3.

FIG. 4 shows the electrical detection apparatus incorporated in amilking claw which comprises an enclosure 14 which is generally circularin plan and divided into four quadrants to provide four independentchambers 15, one of which is shown fully in section in FIG. 4. Theenclosure 14 is formed from two separable components, a base plate 16and a cap 17.

Each of the four chambers 15 has an inlet pipe 18 and a removable outletpipe 19 for connection respectively to a tube which leads to a knownteat cup (not shown) to be applied to the teat of a cow for milking and,on the outlet side, to a tube leading to the milk collection tank.

Screw threaded into a hole in the base plate 16 in each chamber 15 is asensor 21 for detecting changes in the electrical conductivity of milkflowing through a chamber 15. The sensor 21 comprises a toroidally wounddrive coil 22 and a substantially identically constructed detector coil23. The coils are wound on rectangular section formers 24 and thewindings extend around the full circumferential extent of the toroids.The coil windings are encapsulated in insulating material and fit withinappropriately toroidally shaped hollow copper cans 25, 26 which areelectrically connected to earth. The drive coil 22 is thus isolated fromthe detector coil 23. Each can has an open end 27, 28 and the cans 25,26 are assembled back-to-back so that the open ends 27 and 28 are remotefrom one another. In this example the copper cans 25 and 26 are spacedapart from one another and the whole assembly encapsulated in insulatingmaterial.

Electrical leads 29, 31 to the coils pass through sealed apertures inmounting boss 32.

In the operating position, the access opening of pipe 19 within thechamber 15 is above the level of the top of the sensor 21 so that whenmilk is flowing through the chamber 15, the sensor 21 will be completelysubmerged. The encapsulated coils are attached to the mounting boss 32on legs 33 so that there is space for the milk to form a closedelectrically conducting loop which threads both of the toroidally woundcoils 22, 23.

The principle of operation of the sensor is as described with referenceto FIGS. 3 and 3a. The construction employing the copper cans andencapsulating insulation provides for minimum direct coupling betweenthe drive coil 22 and the detection coil 23.

The electronic components and circuits for driving the sensor 21 anddetecting the output signals are illustrated in FIGS. 5 to 7.

Referring to FIG. 5, output from the detection coil 23 is connectedacross a tuning capacitor C1 to an operational amplifier OA1 providing again of approximately 100. Output from the operational amplifier OA1 isfed on line L1 to detection circuitry described further below, and online L2 to a circuit which controls the drive to the drive coil 22.

All of the operational amplifiers shown in FIGS. 5 to 7 are provided, inconventional manner, with connections to a positive supply and anegative supply. These connections have been omitted from the diagramsto avoid unnecessary complication. However, in FIG. 5 an inset labelledcircuit M1 illustrates the supply lines which, in this example, areprovided at +15 and -15 volts relative to the ground line. As indicated,it may be desirable to include smoothing capacitors in the supplycircuit. It will thus be appreciated that the operational amplifiers arecapable of providing an output which can vary between -15 volts and +15volts relative to the ground line.

The signal on line L2 is applied to operational amplifier OA2 set up asa high gain amplifier operating effectively as a switch. The output fromoperational amplifier OA2 is applied across Zener diodes Z1 and Z2connected back-to-back. The drive coil 22 together with its parallelconnected tuning capacitor C2 is connected across the back-to-back Zenerdiodes Z1 and Z2.

When switched on, any initial signal detected from the detection coil 23will be at the resonant frequency of this coil together with capacitorC1. Consequently the signal on line L2 will cause amplifier OA2 toswitch at this frequency. The Zener diodes Z1 and Z2 are thereforedriven alternately to breakdown and the output applied across the drivecoil 22 is a square wave of amplitude equal to twice the breakdownvoltage of the Zener diodes and frequency equal to the resonantfrequency of the detection coil 23. This circuit arrangement thusprovides that the frequency of the drive is held locked to the resonantfrequency of the tuned circuit formed by the detection coil 23 togetherwith the tuning capacitor C1 and will follow changes should there be anyas a consequence of changes in the operating conditions of the sensor21.

The voltage of the output signal from the detection coil 23 is dependentupon the coupling between the drive coil 22 and detection coil 23 whichis in turn dependent upon the conductivity of the milk. The outputvoltage from the detection coil 23 thus provides an indication ofconductivity. The sensitivity of this indication is at a maximum whenthe detection coil 23 is operating at resonance. However, when operatingin this way at resonance, any slight departure from the resonantfrequency will affect significantly the output voltage. It is thus ofcritical importance that the frequency of the drive is held at theresonance frequency of the detection coil circuit. In this context, itis preferable for the resonant frequency of the resonant circuit formedby the drive coil 22 and tuning capacitor C2 to match that of thedetection coil 23 and tuning capacitor C1. However, this is not criticalsince the resonant frequency of the drive coil circuit affects theefficiency with which the drive signal is coupled but will not affectthe frequency of the drive signal.

Turning now to the detection circuitry, the signal on line L1 isconverted to a direct voltage, indicative of the conductivity of themilk, by a half wave rectifier comprising operational amplifier OA3 andassociated diodes D1 and D2, the direct negative feedback via diode D1effectively cutting off the negative half cycle.

The rectified signal is smoothed by the combination of resistor R3 andcapacitor C3 and the output buffered by operational amplifier OA4. FIG.6 shows the continuation of the circuit, with this output on line L3being combined at a summing point P with a voltage from operationalamplifier OA5, the value of which is adjustable by variable resistor VR1as a zero offset. A further operational amplifier OA6 with variableresistor VR2 in the feedback path provides for scale adjustment andfinal output from sensor 21 at point A1.

Each sensor in each of the quadrants of the claw 14 is provided withidentical electronic circuitry from detection coil to output A1. Thecorresponding outputs are shown on FIG. 6 labelled A2, A3, A4. These aresummed and an average generated by operational amplifier OA7 to providea reference output on line L4.

For each channel, a comparator OA8, as shown in FIG. 7, is provided andthe reference level on L4 compared with the output, shown for A1 in FIG.7. The comparator OA8 is set up so that lamp LP is illuminated when thesignal on Line A1 differs by more than a predetermined amount from thelevel on line L4.

For operation, the apparatus is initially set up with a liquid in eachof the chambers 15 having an electrical conductivity less than is likelyto be encountered in the test medium (milk). In each channel, variableresistor VR1 is adjusted to give a scale zero readout. The liquid ineach channel is then replaced with a liquid having a conductivity inexcess of the maximum expected. In each channel the variable resistorVR2 is adjusted to give a maximum scale deflection. After cleaning, theapparatus is then ready for operation on milk. The reference level on L4will represent the average conductivity of the milk passing through thefour chambers 15. If any one chamber 15 receives milk at a conductivitylevel differing significantly from the average, then the appropriatelamp LP(5) for that channel will light up.

It will be appreciated that alternatively, or additionally, an outputfrom comparator OA8 may be used to drive a control valve in the outletpipe 19 to divert milk away from them in collection tank in the eventthat the sensor in that chamber is indicating a level of conductivitydiffering from the average by more than a pre-determined amount.

FIG. 8 illustrates in diagrammatic form a modification of thearrangement shown in FIG. 4. Those components which are the same asthose shown in FIG. 4 carry the same reference numerals. The section hasbeen extended to show two of the four sensors 21 and two of the inletpipes 18.

In this modification, the claw has an upper chamber 15 and a lowerchamber 51. The upper chamber is not divided into separate quadrants,but each sensor 21 is positioned within a cylindrical pot 52. Each inletpipe 18 is positioned so as to be directly over the respective pot 52.An outlet pipe 53 leads from the upper chamber 15 to a dump bucket ordrain. The lower chamber 51 has an outlet pipe 54 leading to the milktreatment device and milk storage tank.

The support boss 32a of each transducer in this modification has acentral aperture 55 providing an outlet opening at the bottom of therespective pot 52. A valve 56 operated by a solenoid 57 is moveable bythe solenoid 57 between a closed position and an open position. In FIG.8, the valve 56 associated with the sensor 21 on the left of the figureis shown in the closed position, whilst the valve on the right hand sideof the figure is shown in the open position.

The solenoids 57 and also the integrated circuit electronics packagemarked IC are accommodated within a recess in the upper part of thechamber 51.

In operation of this modified apparatus, the valves 56 are all initiallyclosed and the first milk to arrive through each of the inlet pipes 18flows into and fills to overflowing the pots 52 containing the sensors21. Overflow milk escapes through the outlet pipe 53.

Conductivity measurement on the milk filling each pot 52 at this stageis carried out as described above with reference to FIGS. 4, 5, 6 and 7.If the measurement for any pot 52 indicates mastitis infection, then thevalve 56 for that particular pot is held closed for the duration of thatmilking session. All the milk from the associated teat is thus directedto the dump bucket or drain via pipe 53. When the flow from inlet pipe18 from that particular teat ceases, remaining milk in the pot 52 drainsslowly out through a small drain hole 58 at the bottom of the pot 52.

Where the test on the initial flow of milk into pot 52 shows normal, thevalve 56 is opened after the initial short period of time necessary forthe test, and the good milk flows into the lower chamber 51 and out tothe cooler and collection tank via pipe 54.

On completion of milking, all valves 56 are opened and cleaning iscarried out by backwashing via pipe 54.

The representation of the integrated circuits IC and the solenoids 57and associated linkages are highly diagrammatic. It will be appreciatedthat any suitable form of valve controlling outflow from the pots 52into the lower chamber 51 may be used. In particular, it is desirable toemploy a valve which can be opened wide to provide a clear and smoothflow path for both the milk flow and, after milking, for the backflowwashing.

The invention is not restricted to the details of the foregoingexamples. For instance, it is not essential to use zener diodes 21 and22 in the drive circuitry shown in FIG. 5. The amplifier OA2, operatingat high gain, is effectively switched at the natural resonance frequencyof the detector circuit. However, the operation of amplifier OA2 is moresatisfactory if the zener diodes are included.

Nor is it essential to provide two separate, grounded copper cans 25,26. An equivalent and effective unitary structure can be provided by apair of co-axial cylinders with a dividing wall extending across thespace between the cylinders perpendicularly to the axis and mid-waybetween the ends of the cylinders. The unitary structure can be madefrom any material of suitably high electrical conductivity.

We claim:
 1. Apparatus for use in the milking of an animal whichcomprises a plurality of inlet paths, a common outlet path, a subsidiaryoutlet path, a respective transducer associated with each inlet path forproviding a quantitative signal representing the magnitude of a propertyof milk in that path, comparison means for comparing the said signal ineach inlet path with a reference, the comparison means providing anoutput signal which identifies the inlet path in which the milk has amagnitude of the said property differing by more than a predeterminedamount from the reference magnitude, and a diverter valve in each of thesaid inlet paths which diverter valve is operable to divert flow fromthe inlet path away from the said common outlet path to the saidsubsidiary outlet path.
 2. Apparatus as claimed in claim 1, whereincontrol means responsive to the said output signal actuate the divertervalve in the input path identified by the output signal to divert flowto the said subsidiary outlet path.
 3. Apparatus as claimed in claim 2wherein the control means operate the diverter valves, during an initialstage of milking to direct milk from all of the inlet paths to thesubsidiary outlet path and, at the end of the initial stage operatessome or all of the valves to direct milk from the corresponding inletpaths to the said common outlet path.
 4. Apparatus as claimed in claim1, wherein reference means generate the said reference as an average ofthe signals representing the respective magnitudes of the property ofthe milk in the inlet paths.
 5. Apparatus as claimed in claim 1, whereinat least one of the transducers is a non-intrusive transducer. 6.Apparatus as claimed in claim 5, wherein the or each transducercomprises a plurality of electromagnetic inductors arranged to beelectromagnetically coupled by milk in the corresponding inlet path. 7.Apparatus as claimed in claim 6, wherein the or each transducercomprises a pair of toroidally wound coils arranged so that the milkforms an electrically conducting loop threading the toroids formed bythe toroidally wound coils.
 8. Apparatus as claimed in claim 7, whereinthe coils are contained in, but electrically insulated from,appropriately toroidally shaped copper containers open at one end in aplane parallel with the plane containing the continuous axis of thetoroid.
 9. Apparatus as claimed in claim 8, wherein the coppercontainers contain respectively a drive coil and a detection coil andare mounted adjacent, but electrically insulated from, one another onthe same major axis but with their respective open ends remote from oneanother.
 10. Apparatus as claimed in claim 9, wherein an electricalpower supply is connected to provide an alternating current drive to thedrive coil and an electrical signal detection circuit is connected todetect the amplitude of the alternating current induced in the detectioncoil.
 11. Apparatus as claimed in claim 10, wherein each coil is acomponent of a resonant circuit and the detection circuit is connectedto control the power supply so as to maintain the frequency of thealternating current drive to the drive coil at or close to the resonantfrequency of the circuit containing the detection coil.
 12. Apparatus asclaimed in claim 1 wherein the magnitude of the reference is derived byreference means during milking from the magnitude of the said propertyof the milk in said plurality of inlet paths.
 13. A method of milking ananimal wherein milk is drawn concurrently from a plurality of teats ofthe animal, a property of milk drawn from each teat is compared duringmilking with the same property of milk drawn from each other teat, and,whilst said property has substantially the same value for all of theteats, the milk drawn from all of the teats is directed along a commondischarge path and, when said comparing step shows that the value ofsaid property of the milk from one teat departs substantially from thevalue of said property of the milk from the other teat or teats, themilk from either the one teat or the milk from the other teat or teatsis diverted from the common discharge path whilst undiverted milkcontinues to flow along the said common discharge path.
 14. A methodaccording to claim 13, wherein, once the milk from the one teat or fromthe other teat or teats has been diverted from the common dischargepath, diversion of the milk from that teat or from the other teat orteats from the common discharge path is maintained, irrespective ofwhether the value of said property of the milk from the one teat revertsto a value substantially the same as the value of that property of themilk from the other teat or teats.
 15. A method according to claim 13,wherein, during an initial stage of milking, milk from all of the teatsis directed to a common, subsidiary discharge path, irrespective of thevalues of said property of the milk from the several teats and, at theend of the initial stage of milking, the milk from all of the teats isdirected to a common main discharge path, unless the value of saidproperty of the milk from one teat departs substantially from the valueof said property of the milk from the other teat or teats, in which casemilk from the one teat continues to be directed to the subsidiarydischarge path.
 16. A method of milking an animal wherein milk is drawnconcurrently from a plurality of teats of the animal, a property of milkdrawn from each teat is compared with a reference magnitude of saidproperty, which reference magnitude is derived during milking from themagnitude of the said property of the milk drawn from the said pluralityof teats, and, when said comparing step shows that the magnitude of saidproperty of the milk from any one of the teats differs by more than apredetermined amount from the reference magnitude, the milk from thesaid one teat or the milk from the other teat or teats is diverted fromthe common discharge path, whilst undiverted milk continues to flowalong the said common discharge path.